Anybody know anything about "Moonmilk?"

David Rosen <drosen at net.bio.net> writes:
>> When visiting Carlsbad Caverns, my tour guide talked a little about
> "Moon-Milk." He said some of the rocks in the deepest part of the cave were
> covered with a milky secretion of bacteria. He claimed that these bacteria are
> chemotropic, i.e., they get their energy from chemical reactions of the rock
> materials rather. I am surprised that they are not heteroetropic, taking
> sustenance from bat droppings somehow. However, this is really just hear-say.
>
I think it was in the next to last American Scientist (sorry I
don't have it with me) there was an article about karst
geological formations, i.e. limestone caves. It was stated that
the New Mexico caverns including Carlsbad were formed when
hydrogen sulfide, migrating from the Texas oil fields, met
oxygenated ground waters in the limestone formations. The
mixture of H2S with an electron acceptor supported a microbial
chemolithotrophic community that generated sulfuric acid. The
sulfuric acid then reacted with the limestone forming calcium sulfate
and carving out the caverns. Is moonmilk possibly a finely
divided calcium or magnesium sulfate mineral produced by this
kind of reaction, possibly encasing the bacterial cells?
----------------------------------------------------------------------
Walter Ogston ogston at hobbes.kzoo.edu
Department of Biology Phone: (616)337-7010
Kalamazoo College Fax: (616)337-7251
Kalamazoo, MI 49006-3295